login code error, session_start()

Question

I am trying to create a login form, I created the html form and wrote this PHP code but I keep on getting an error about session_start(); and header already sent

The error:

Warning: session_start(): Cannot send session cookie - headers already sent by

<?php
session_start();
if($_POST['submit'])
{
include_once('my_connection.php');
$username = strip_tags($_POST['username']);
$password = strip_tags($_POST['password']);

$sql = "SELECT id,username,password FROM users WHERE username = '$username'  AND password = '$password'";
$query = mysqli_query($connect,$sql);
if($query) {
$row = mysqli_fetch_row($query);
$id = $row[0];
$dbusername = $row[1];
$dbpassword = $row[2];
if($username == $dbusername && $password == $dbpassword)
{
    $_SESSION['username'] = $username;
    $_SESSION['id'] =$id;
    header('Location:home.php');
}else {

    echo "Incorrect username or password.";
} } }?>

I put the session_start() on the top of the code but still don't work

Is this the entire file? Are you sure you don't have any output before the PHP code? — Chris, Mar 22 '16 at 09:49
@Chris yes I'm sure , I have after the php code an html code but before there is nothing. — Maram Al-Zu'bi, Mar 22 '16 at 09:50
@IswantoSan Warning: session_start(): Cannot send session cookie - headers already sent by — Maram Al-Zu'bi, Mar 22 '16 at 09:50
@MaramAl-Zu'bi And this file is being accessed directly, not included in another file? — Chris, Mar 22 '16 at 09:51
@Chris the session_start error is gone but still have "Warning: Cannot modify header information - headers already sent by .. — Maram Al-Zu'bi, Mar 22 '16 at 09:54
I want the user after logging in to be redirected into another page, that's why I used the header Location .. Can anyone explain to me why I keep getting this error? — Maram Al-Zu'bi, Mar 22 '16 at 09:58
You should really be hashing passwords that are stored on a database see `password_hash()` and `password_verify()` — RiggsFolly, Mar 22 '16 at 10:02
@MaramAl-Zu'bi What did you do to stop the `session_start()` error! — RiggsFolly, Mar 22 '16 at 10:05
@MaramAl-Zu'bi have tried putting ob_start() at the top of your page? — Rafique Mohammed, Mar 22 '16 at 10:12

score 1 · Answer 1 · edited May 23 '17 at 11:45

Warning: session_start(): Cannot send session cookie

To start with, always have your start_session() at the top. Yes, adding ob_start() above it may fix it and adding ob_flush() at the bottom could but it looks like it hasn't so:

If you're requiring the same file or another file, ensure the file you're requiring does not have a session_start() function within it. Ensure you have no duplicates of session_start() anywhere else either in the same code.

Also, a big reason actually may be because you're missing syntax in your header() and the program is not finishing/ending, only requiring.

Change it to this:

header('Location: home.php');
exit;

Sources to further help you:

Source 1
Source 2

login code error, session_start()

1 Answers1